Toward Isoprene Measurements from CrIS: A First Look over Two Isoprene Hot Spots

Isoprene is the dominant non-methane VOC emitted to the atmosphere, and plays a key role in ozone chemistry, reactive nitrogen cycling, secondary aerosol formation, and the oxidizing capacity of the atmosphere. Bottom-up estimates of global isoprene emissions are uncertain as they are based on sparse measurements and are highly sensitive to uncertainties in underlying emission drivers such as land cover and meteorology. Space-based measurements of formaldehyde can be used as a top-down constraint, but the approach is limited by the fact that formaldehyde is also produced by VOCs other than isoprene. Here we present our progress in developing the first space-based measurements of isoprene, from the CRoss-track Infrared Sounder (CrIS) onboard Suomi-NPP. Satellite measurements of isoprene itself will offer direct space-based constraints on fluxes from the world’s major isoprene source regions. We evaluate initial CrIS retrievals over two isoprene hot spots, the Southeastern US in summertime and the Amazon, using a combination of airborne measurements and chemical transport model (GEOS-Chem CTM) simulations. We also present an assessment of the dominant measurement uncertainties and the role of interferences using a synthetic retrieval approach.